The present invention relates to non-metallic materials and more particularly to heat sensitive non-metallic materials.
Non-metallic, heat sensitive surfaces such as polyvinyl chloride house siding absorb solar energy upon exposure to the sun and exhibit polymeric degradation after extended periods. This effect is particularly pronounced when the polyvinyl chloride is pigmented in dark colors such as brown. The degradation spoken of can be a partial or total loss of structural integrity, a darkening or discoloration of the product, a loss of flexibility of resilience, loss of shape due to softening or any combination of these effects.
These difficulties have been typically dealt with by forming an extruded composite which is made by forming a protective coextruded layer of molding composition on the outside surface of the polyvinyl chloride structural member. This protective molding composition i.e., capstock, has been pigmented with infrared reflective pigments which serve to reduce heat absorption and, therefore, reduce the temperature rise in the polyvinyl chloride structural member. Examples of this art recognized manner of protecting heat sensitive building substrates can be found in G.B. No. 1,444,563 and G.B. No. 1,572,728. Also, exemplary is U.S. Pat. No. 4,424,292 which is directed to an improved vinyl polymer composition containing an effective amount of an infrared reflecting black pigment made up of a mixture of chromic oxide and ferric oxide. This patent discloses both the extruded composite described above as well as conventional compression or injection molded members which contain the pigments in the polyvinyl chloride composition.
The aforedescribed art-recognized methods have a variety of disadvantages, among them the fact that color choices are extremely limited. This is a need, therefore, for a more efficient way of reducing the heating of heat sensitive surfaces, particularly those which are darkly pigmented, upon prolonged exposure to infrared and ultraviolet light.